I bet it is gasket 34, 36 leaking. They've been replaced by a new metal one piece.

 

A new cam bearing will add very little to the cost, especially with the top-end already off and if it's worn, that can cause some vibration. You can spend as much money as want with upgrades, but you don't have to! Putting it back to factory specs won't "rob the bank" and will give you just as many trouble-free miles.

 

It look like a rocker box base gasket. We've a few in the shop lately that were pinched when installed and can't quite figure out why they didn't leak sooner. 50K is a good time to freshen up the engine. You might want to include an S&S reed valve breather as they are easier on the gaskets. The most common cause for gasket failure is failure to allow the engine to warm up fully before putting a load on it. The cylinders grow about .040" and taht put the full clamping load on the gaskets. Hope this helps. Putting an Ultima engine in is a good idea as you can still freshen up the original at your leisure and sell it and re-coup some of your cash making just as cheap to install a new engine as rebuilding your old one. Just some food for thought.

 

Motor mounts. They are also on the list of things that 'don't last forever'. Most likely the front, which tends to get soaked with oil doing oil changes.
You can get all that, and a big 'smile' by going to a SE air filter, an aftermarket cam, and a decent exhaust. Trust me, there was a WORLD of difference in my bike when I put the SE air cleaner and SuperTrapp slipons on. Even more when I had the EV27 cam and Torrington bearing installed. And even more when I took it to a shop where they could dynotune the carb and installed a Dyna igniton.

On all (stock) EVO's there are two simple things to think about in order to improve performance: Air In, Exhaust Out. The MoCo had them so restricted due to EPA standards, that they were breathing/exhaling though a blanket.

I'd have to look up the 'numbers' on my EVO, but offhand they were in the range of 80/85 HP/TQ when it was last dyno'd. I average (HWY) in the high 40's as far as MPG goes.

The base gasket issue, like I posted, is just a bad design by The MoCo. The oil returns from the rockerboxes, through the heads and cylinders via a hole cast/bored through the length of the head and cylinder. This 'hole' sit over top of another 'hole' in the crankcase. The only thing to prevent oil from seeping, weeping, leaking is a gasket. In addition to the cylinder/case expanding with heat at different rates, the cylinders will 'rock' ever so slightly. All causing failure of the gasket. If you have to ask why it doesn't leak 'up top' (between the head/cylinder), it's because the cylinder head gasket is better. Although, a blown head gasket is always a possibility.

Harley actually changed the base gasket design, sometime in early-mid 90's, due to numerous complaints about leakage (it was probably the number 1 'topic' back then). If you bitched long/hard enough, The MoCo would replace them (think silent recall).

Why in the world HD didn't press fit a small tube or bushing into the cylinder, I have no idea. Maybe they had concerns about it working loose and ending up in the crankcase. However, they could've step bored the case to prevent that. In the end, it was probably just an issue of $$$ during the mfg process.

And they must've really thought that base gasket would hold. Mine did: For one year. The limit of the OEM warranty.

 

Here's the "estimate" from my indy, based on what I told him over the phone:
R&R top end and cyl's, repair oil leak, mic components, repair as needed. 450.00
R&R cam to inspect/replace cam brng. 75.00
Dissassemble heads to clean & inspect, measure valve to guide clearance, spring pressure. 75.

Wiseco piston set 200
top end gasket 109
cam brng 7
ev 27 cam 165
ez adjust push rod set 130-160

bore 2 cyls w/torque plates. 110
valve job w/no new valves 100
lifters if needed are 80-90ea

My remaining questions are:
If I indeed have oil blow-by, is it likely that can be fixed without putting in new pistons and doing the valve job, as long as they aren't too worn? If I need pistons, should I request an HD part or something else for less money? (he already has the Wiseco..whatever that is).
Can I pass on the adjustable push-rod set? I think I'll pass on getting a new cam, unless there's an issue with the stocker. I'm not a mechanic, so this is mostly new to me

I have confidence the guy knows what he's doing. He has pics in his fab shop of him nitro-racing Harleys, and he's still actively racing on weekends. He did a good job tuning my carb and doing some other maintenance items, for a very reasonable price.

 

Blow by is from worn rings/cylinders. Wiseco pistons have a good reputation, they've been around automotive circles a long time. If he's used them and is comfortable, I'd consider that or OEM. You will likely need either new HD fixed pushrods or the adjustables if anything is done to the valves or cam. I'd go with the adjustables, so I wouldn't consider that optional if you get the top end job done. If you need lifters, get the OEM ones, and I'm pretty sure they are well under that price.

All motors will have some blow by. How much are we talking about here? Is the compression good? Does it burn oil? If it isn't too bad, I'd just consider replacing the rocker box gaskets and that cam bearing and leave the rest alone. 75 to 100K on an Evo top end is not unusual. If your cam is shot, which it might be at 50K, then put in a new one, new lifters and adjustable pushrods. Otherwise, leave it alone.

 

If I switch back to a dino oil, is there a chance the oil leaks will slow down?

 

(update) It WAS 34, 36 leaking. I replaced them today myself. It was not a difficult job, and it was neat to see the boxes off. I took a short ride afterward and so far, no leaks. I used HD gaskets.

Thanks all for your input! Hopefully I have plenty of time until I need a rebuild.